This is an open label, randomized, multicenter clinical study of oral RFS 2000 in colorectal cancer patients who have failed one previous 5-FU based chemotherapy. Patients will receive eight weeks (one cycle) of RFS 2000, administered on a seven day schedule given orally for the first five consecutive days of the cycle followed by two days rest. Eligible patients will have evidence of persistent disease. The daily dose of RFS 2000 will be 1.5 mg/m2. Patients who experience disease stabilization or regression after the completion of one cycle of RFS 2000 treatment will receive additional courses of treatment. If therapy is delayed for >3 weeks patients will be taken off study. Forty-five evaluable adult patients are to be enrolled. The primary objectives of the study are: 1)To determine the objective relsponse rate of the treatment regiments. 2)To evaluate the safety and toxicity of the treatment regimen.